Method and apparatus for currency discrimination

ABSTRACT

An improved method of generating a master pattern corresponding to a given denomination for use in a discrimination system capable of discriminating among currency bills of different denominations. The method comprises the steps of generating a plurality of component patterns for a given denomination by scanning at least one genuine bill of the given denomination and generating a master pattern for the given denomination. The master pattern is derived from an average of the component patterns. The component patterns represent analog variations in characteristic information detected from a genuine bill during scanning. The master pattern represents an average of analog variations of the characteristic information for the given denomination.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 08/127,334 filed Sep. 27, 1993, now U.S. Pat. No. 5,467,405,for a "Method and Apparatus for Currency Discrimination and Counting"and a continuation-in-part of U.S. patent application Ser. No.08/219,093 filed Mar. 29, 1994, now abandoned, for a "CurrencyDiscriminator and Authenticator," said U.S. patent application Ser. No.08/127,334 is a continuation of U.S. patent application Ser. No.07/885,648, filed on May 19, 1992, and issued as U.S. Pat. No.5,295,196, for a "Method and Apparatus for Currency Discrimination andCounting," which is a continuation-in-part of abandoned U.S. patentapplication Ser. No. 07/475,111, filed Feb. 5, 1990, for a "Method andApparatus for Currency Discrimination and Counting," said U.S. patentapplication Ser. No. 08/219,093 is a continuation-in-part of U.S. patentapplication Ser. No. 08/127,334 filed Sep. 27, 1993, for a "Method andApparatus for Currency Discrimination and Counting", which is acontinuation of U.S. patent application Ser. No. 07/885,648, filed onMay 19, 1992, and issued as U.S. Pat. No. 5,295,196, for a "Method andApparatus for Currency Discrimination and Counting," which is acontinuation-in-part of abandoned U.S. patent application Ser. No.07/475,111, filed Feb. 5, 1990, for a "Method and Apparatus for CurrencyDiscrimination and Counting."

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates, in general, to currency identification.More specifically, the present invention relates to an apparatus andmethod for discriminating currency bills of different denominations.

2. Background

A variety of techniques and apparatus have been used to satisfy therequirements of automated currency handling systems. At the lower end ofsophistication in this area of technology are systems capable ofhandling only a specific type of currency, such as a specific dollardenomination, while rejecting all other currency types. At the upper endare complex systems which are capable of identifying and discriminatingamong and automatically counting multiple currency denominations.

Currency discrimination systems typically employ either magnetic sensingor optical sensing for discriminating among different currencydenominations. Magnetic sensing is based on detecting the presence orabsence of magnetic ink in portions of the printed indicia on thecurrency by using magnetic sensors, usually ferrite core-based sensors,and using the detected magnetic signals, after undergoing analog ordigital processing, as the basis for currency discrimination. A varietyof currency characteristics can be measured using magnetic sensing.These include detection of patterns of changes in magnetic flux,patterns of vertical grid lines in the portrait area of bills, thepresence of a security thread, total amount of magnetizable material ofa bill, patterns from sensing the strength of magnetic fields along abill, and other patterns and counts from scanning different portions ofthe bill such as the area in which the denomination is written out.

The more commonly used optical sensing techniques, on the other hand,are based on detecting and analyzing variations in light reflectance ortransmissivity characteristics occurring when a currency bill isilluminated and scanned by a strip of focused light. The subsequentcurrency discrimination is based on the comparison of sensed opticalcharacteristics with prestored parameters for different currencydenominations, while accounting for adequate tolerances reflectingdifferences among individual bills of a given denomination. A variety ofcurrency characteristics can be measured using optical sensing. Theseinclude detection of a bill's density, color, length and thickness, thepresence of a security thread and holes, and other patterns ofreflectance and transmission. Color detection techniques may employcolor filters, colored lamps, and/or dichroic beamsplitters.

In addition to magnetic and optical sensing, other techniques ofdetecting characteristic information of currency include electricalconductivity sensing, capacitive sensing (such as for watermarks,security threads, thickness, and various dielectric properties) andmechanical sensing (such as for limpness and thickness).

A major obstacle in implementing automated currency discriminationsystems is obtaining an optimum compromise between the criteria used toadequately define the characteristic pattern for a particular currencydenomination, the time required to analyze test data and compare it topredefined parameters in order to identify the currency bill underscrutiny, and the rate at which successive currency bills may bemechanically fed through and scanned. Even with the use ofmicroprocessors for processing the test data resulting from the scanningof a bill, a finite amount of time is required for acquiring samples andfor the process of comparing the test data to stored parameters toidentify the denomination of the bill.

Recent currency discriminating systems rely on comparisons between ascanned pattern obtained from a subject bill and sets of stored masterpatterns for the various denominations among which the system isdesigned to discriminate. As a result, the master patterns which arestored play an important role in a discrimination system's ability todiscriminate among bills of various denominations as well as betweengenuine bills and counterfeit bills. These master patterns have beengenerated by scanning bills of various denominations known to be genuineand storing the resulting patterns. However, a pattern generated byscanning a genuine bill of a given denomination can vary depending upona number of factors such as the condition of the bill, e.g., whether itis a crisp bill in new condition or a worn, flimsy bill, as well as yearin which the bill was printed, e.g., before or after security threadswere incorporated into bills of some denominations. Likewise, it hasbeen found that bills which have experienced a high degree of usage mayshrink, resulting in a reduction of the dimensions of such bills. Suchshrinkage may likewise result in variations in scanning patterns. As aresult, if, for example, a $20 master pattern is generated by scanning acrisp, genuine $20 bill, the discrimination system may reject anunacceptable number of genuine but worn $20 bills. Likewise, if a $20master pattern is generated using a very worn, genuine $20 bill, thediscrimination system may reject an unacceptable number of genuine butcrisp $20 bills.

SUMMARY OF THE INVENTION

It is a principal object of the present invention to provide an improvedmethod and apparatus for discriminating among currency bills comprisinga plurality of currency denominations.

It is another object of this invention to provide an improved method andapparatus of the above kind which is capable of efficientlydiscriminating among bills of several currency denominations at a highspeed and with a high degree of accuracy.

Briefly, in accordance with the present invention, the objectivesenumerated above are achieved by generating a master pattern for a givendenomination by averaging a plurality of component patterns, typicallythree, each generated by scanning a genuine bill of the givendenomination.

According to one method, a master pattern for a given denomination isgenerated by averaging a plurality of component patterns, wherein thecomponent patterns are generated by scanning one or more genuine billsof "standard" or average quality of the given denomination. A "standard"bill is a slightly used bill, as opposed to a crisp new bill or onewhich has been subject to a high degree of usage.

According to another method, a master pattern for a given denominationis generated by averaging a plurality of component patterns, whereinsome of the component patterns are generated by scanning one or more newbills of the given denomination and some of the component patterns aregenerated by scanning one or more old bills of the given denomination.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparent uponreading the following detailed description in conjunction with thedrawings in which:

FIG. 1 is a functional block diagram illustrating a preferred embodimentof a currency discriminating system according to the present invention;

FIG. 2A is a diagrammatic perspective illustration of the successiveareas scanned during the traversing movement of a single bill across anoptical sensor according to a preferred embodiment of the presentinvention;

FIG. 2B is a perspective view of a bill and a preferred area to beoptically scanned on the bill;

FIG. 2C is a diagrammatic side elevation view of the scan area to beoptically scanned on a bill according to a preferred embodiment of thepresent invention;

FIG. 3A is a block diagram illustrating a preferred circuit arrangementfor processing and correlating reflectance data according to the opticalsensing and counting technique of this invention;

FIG. 3B is a block diagram illustrating a circuit arrangement forproducing a reset signal;

FIGS. 4A-4C are graphs illustrating master patterns generated accordingto a first method according to a preferred embodiment of the presentinvention;

FIG. 5A is a graph illustrating component patterns generated by scanningold and new $20 bills according a second method according to a preferredembodiment of the present invention; and

FIG. 5B is a graph illustrating an pattern for a $20 bill scanned in theforward direction derived by averaging the patterns of FIG. 5A accordinga second method according to a preferred embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, there is shown a functional block diagramillustrating a preferred embodiment of a currency discriminating systemaccording to the present invention. The system 10 includes a billaccepting station 12 where stacks of currency bills that need to beidentified and counted are positioned. Accepted bills are acted upon bya bill separating station 14 which functions to pick out or separate onebill at a time for being sequentially relayed by a bill transportmechanism 16, according to a precisely predetermined transport path,across scanhead 18 where the currency denomination of the bill isscanned and identified. In the preferred embodiment depicted, scanhead18 is an optical scanhead that scans for characteristic information froma scanned bill 17 which is used to identify the denomination of thebill. The scanned bill 17 is then transported to a bill stacking station20 where bills so processed are stacked for subsequent removal.

The optical scanhead 18 of the preferred embodiment depicted in FIG. 1comprises at least one light source 22 directing a beam of coherentlight downwardly onto the bill transport path so as to illuminate asubstantially rectangular light strip 24 upon a currency bill 17positioned on the transport path below the scanhead 18. Light reflectedoff the illuminated strip 24 is sensed by a photodetector 26 positioneddirectly above the strip. The analog output of photodetector 26 isconverted into a digital signal by means of an analog-to-digital (ADC)convertor unit 28 whose output is fed as a digital input to a centralprocessing unit (CPU) 30.

While scanhead 18 in the preferred embodiment of FIG. 1 is an opticalscanhead, it should be understood that it may be designed to detect avariety of characteristic information from currency bills. Additionally,the scanhead may employ a variety of detection means such as magnetic,optical, electrical conductivity, and capacitive sensors. Use of suchsensors is discussed in more detail U.S. patent application Ser. No.08/219,093 filed on Mar. 28, 1994, now abandoned, for a "CurrencyDiscriminator and Authenticator" and incorporated herein by reference.

Referring again to the preferred embodiment depicted in FIG. 1, the billtransport path is defined in such a way that the transport mechanism 16moves currency bills with the narrow dimension of the bills beingparallel to the transport path and the scan direction. Alternatively,the system 10 may be designed to scan bills along their long dimensionor along a skewed dimension. As a bill 17 moves on the transport path onthe scanhead 18, the coherent light strip 24 effectively scans the billacross the narrow dimension of the bill. In the preferred embodimentdepicted, the transport path is so arranged that a currency bill 17 isscanned by scanhead 18 approximately about the central section of thebill along its narrow dimension, as shown in FIG. 1. The scanhead 18functions to detect light reflected from the bill as it moves across theilluminated light strip 24 and to provide an analog representation ofthe variation in light so reflected which, in turn, represents thevariation in the dark and light content of the printed pattern orindicia on the surface of the bill. This variation in light reflectedfrom the narrow dimension scanning of the bills serves as a measure fordistinguishing, with a high degree of confidence, among a plurality ofcurrency denominations which the system of this invention is programmedto handle.

A series of such detected reflectance signals are obtained across thenarrow dimension of the bill, or across a selected segment thereof, andthe resulting analog signals are digitized under control of the CPU 30to yield a fixed number of digital reflectance data samples. The datasamples are then subjected to a digitizing process which includes anormalizing routine for processing the sampled data for improvedcorrelation and for smoothing out variations due to "contrast"fluctuations in the printed pattern existing on the bill surface. Thenormalized reflectance data so digitized represents a characteristicpattern that is fairly unique for a given bill denomination and providessufficient distinguishing features among characteristic patterns fordifferent currency denominations. This process is more fully explainedin U.S. patent application Ser. No. 07/885,648, filed on May 19, 1992,now issued as U.S. Pat. No. 5,295,196 for a "Method and Apparatus forCurrency Discrimination and Counting," which is incorporated herein byreference in its entirety.

In order to ensure strict correspondence between reflectance samplesobtained by narrow dimension scanning of successive bills, theinitiation of the reflectance sampling process is preferably controlledthrough the CPU 30 by means of an optical encoder 32 which is linked tothe bill transport mechanism 16 and precisely tracks the physicalmovement of the bill 17 across the scanhead 18. More specifically, theoptical encoder 32 is linked to the rotary motion of the drive motorwhich generates the movement imparted to the bill as it is relayed alongthe transport path. In addition, the mechanics of the feed mechanism(not shown, see U.S. Pat. No. 5,295,196 referred to above) ensure thatpositive contact is maintained between the bill and the transport path,particularly when the bill is being scanned by scanhead 18. Under theseconditions, the optical encoder 32 is capable of precisely tracking themovement of the bill 17 relative to the light strip 24 generated by thescanhead 18 by monitoring the rotary motion of the drive motor.

The output of photodetector 26 is monitored by the CPU 30 to initiallydetect the presence of the bill underneath the scanhead 18 and,subsequently, to detect the starting point of the printed pattern on theBill, as represented by the thin borderline 17A which typically enclosesthe printed indicia on currency bills. Once the borderline 17A has beendetected, the optical encoder 32 is used to control the timing andnumber of reflectance samples that are obtained from the output of thephotodetector 26 as the bill 17 moves across the scanhead 18 and isscanned along its narrow dimension.

The detection of the borderline 17A constitutes an important step andrealizes improved discrimination efficiency since the borderline 17Aserves as an absolute reference point for initiation of sampling. If theedge of a bill were to be used as a reference point, relativedisplacement of sampling points can occur because of the random mannerin which the distance from the edge to the borderline 17A varies frombill to bill due to the relatively large range of tolerances permittedduring printing and cutting of currency bills. As a result, it becomesdifficult to establish direct correspondence between sample points insuccessive bill scans and the discrimination efficiency is adverselyaffected.

The use of the optical encoder 32 for controlling the sampling processrelative to the physical movement of a bill 17 across the scanhead 18 isalso advantageous in that the encoder 32 can be used to provide apredetermined delay following detection of the borderline prior toinitiation of samples. The encoder delay can be adjusted in such a waythat the bill 17 is scanned only across those segments along its narrowdimension which contain the most distinguishable printed indiciarelative to the different currency denominations.

In the case of U.S. currency, for instance, it has been determined thatthe central, approximately two-inch portion of currency bills, asscanned across the central section of the narrow dimension of the bill,provides sufficient data for distinguishing among the various U.S.currency denominations on the basis of the correlation techniquedisclosed in U.S. Pat. No. 5,295,196 referred to above. Accordingly, theoptical encoder can be used to control the scanning process so thatreflectance samples are taken for a set period of time and only after acertain period of time has elapsed since the borderline 17A has beendetected, thereby restricting the scanning to the desired centralportion of the narrow dimension of the bill.

FIGS. 2A-2C illustrate the scanning process of scanhead 20 in moredetail. Referring to FIG. 2B, as a bill 17 is advanced in a directionparallel to the narrow edges of the bill, scanning via a wide slit inthe scanhead 18 is effected along a segment S of the central portion ofthe bill 17. This segment S begins a fixed distance d inboard of theborderline 17A. As the bill 17 traverses the scanhead 18, a strip s ofthe segment S is always illuminated, and the photodetector 26 produces acontinuous output signal which is proportional to the intensity of thelight reflected from the illuminated strip s at any given instant. Thisoutput is sampled at intervals controlled by the encoder, so that thesampling intervals are precisely synchronized with the movement of thebill across the scanhead 18.

As illustrated in FIGS. 2A and 2C, it is preferred that the samplingintervals be selected so that the strips s that are illuminated forsuccessive samples overlap one another. The odd-numbered andeven-numbered sample strips have been separated in FIGS. 2A and 2C tomore clearly illustrate this overlap. For example, the first and secondstrips s1 and s2 overlap each other, the second and third strips s2 ands3 overlap each other, and so on. Each adjacent pair of strips overlapeach other. In the illustrative example, this is accomplished bysampling strips that are 0.050 inch wide at 0.029 inch intervals, alonga segment S that is 1.83 inch long (64 samples).

The optical sensing and correlation technique is based upon using theabove process to generate a series of stored intensity signal patternsusing genuine bills for each denomination of currency that is to bedetected. According to a preferred embodiment, two or four sets ofmaster intensity signal samples are generated and stored within systemmemory, preferably in the form of an EPROM 34 (see FIG. 1), for eachdetectable currency denomination. The sets of master intensity signalsamples for each bill are generated from optical scans, performed on thegreen surface of the bill and taken along both the "forward" and"reverse" directions relative to the pattern printed on the bill.Alternatively, the optical scanning may be performed on the black sideof U.S. currency bills or on either surface of foreign bills.Additionally, the optical scanning may be performed on both sides of abill, for example, by placing a scanhead on each side of the billtransport path as described in more detail in co-pending U.S. patentapplication Ser. No. 08/207,592 filed Mar. 8, 1994, now U.S. Pat. No.5,467,406, for a "Method and Apparatus for Currency Discrimination."

In adapting this technique to U.S. currency, for example, sets of storedintensity signal samples are generated and stored for seven differentdenominations of U.S. currency, i.e., $1, $2, $5, $10, $20 , $50 and$100. For bills which produce significant pattern changes when shiftedslightly to the left or right, such as the $2 and the $10 bill in U.S.currency, it is preferred to store two patterns for each of the"forward" and "reverse" directions, each pair of patterns for the samedirection represent two scan areas that are slightly displaced from eachother along the long dimension of the bill. Accordingly, a set of 18different master characteristic patterns is stored within the systemmemory for subsequent correlation purposes (four master patterns for the$2 and the $10 bill and two master patterns for each of the otherdenominations. The generation of the master patterns will be discussedin more detail below. Once the master patterns have been stored, thepattern generated by scanning a bill under test is compared by the CPU30 with each of the 18 master patterns of stored intensity signalsamples to generate, for each comparison, a correlation numberrepresenting the extent of correlation, i.e., similarity betweencorresponding ones of the plurality of data samples, for the sets ofdata being compared.

The CPU 30 is programmed to identify the denomination of the scannedbill as corresponding to the set of stored intensity signal samples forwhich the correlation number resulting from pattern comparison is foundto be the highest. In order to preclude the possibility ofmischaracterizing the denomination of a scanned bill, as well as toreduce the possibility of spurious notes being identified as belongingto a valid denomination, a bi-level threshold of correlation is used asthe basis for making a "positive" call. Such a method is disclosed inU.S. Pat. No. 5,295,196 referred to above. If a "positive" call can notbe made for a scanned bill, an error signal is generated.

Using the above sensing and correlation approach, the CPU 30 isprogrammed to count the number of bills belonging to a particularcurrency denomination as part of a given set of bills that have beenscanned for a given scan batch, and to determine the aggregate total ofthe currency amount represented by the bills scanned during a scanbatch. The CPU 30 is also linked to an output unit 36 which is adaptedto provide a display of the number of bills counted, the breakdown ofthe bills in terms of currency denomination, and the aggregate total ofthe currency value represented by counted bills. The output unit 36 canalso be adapted to provide a print-out of the displayed information in adesired format.

Referring now to FIG. 3A, there is shown a representation, in blockdiagram form, of a preferred circuit arrangement for processing andcorrelating reflectance data according to the system of this invention.As shown therein, the CPU 30 accepts and processes a variety of inputsignals including those from the optical encoder 32, the photodetector26 and a memory unit 38, which can be an erasable programmable read onlymemory (EPROM). The memory unit 38 has stored within it the correlationprogram on the basis of which patterns are generated and test patternscompared with stored master programs in order to identify thedenomination of test currency. A crystal 40 serves as the time base forthe CPU 30, which is also provided with an external reference voltageV_(REF) on the basis of which peak detection of sensed reflectance datais performed, as explained in detail below.

The CPU 30 also accepts a timer reset signal from a reset unit 44 which,as shown in FIG. 3B, accepts the output voltage from the photodetector26 and compares it, by means of a threshold detector 44A, relative to apre-set voltage threshold, typically 5.0 volts, to provide a resetsignal which goes "high" when a reflectance value corresponding to thepresence of paper is sensed. More specifically, reflectance sampling isbased on the premise that no portion of the illuminated light strip (24in FIG. I) is reflected to the photodetector in the absence of a billpositioned below the scanhead. Under these conditions, the output of thephotodetector represents a "dark" or "zero" level reading. Thephotodetector output changes to a "white" reading, typically set to havea value of about 5.0 volts, when the edge of a bill first becomespositioned below the scanhead and falls under the light strip 24. Whenthis occurs, the reset unit 44 provides a "high" signal to the CPU 30and marks the initiation of the scanning procedure.

In accordance with a feature of this invention, the machine-directiondimension of the illuminated strip of light produced by the lightsources within the scanhead is set to be relatively small for theinitial stage of the scan when the thin borderline is being detected.The use of the narrow slit increases the sensitivity with which thereflected light is detected and allows minute variations in the "gray"level reflected off the bill surface to be sensed. This is important inensuring that the thin borderline of the pattern, i.e., the startingpoint of the printed pattern on the bill, is accurately detected. Oncethe borderline has been detected, subsequent reflectance sampling isperformed on the basis of a relatively wider light strip in order tocompletely scan across the narrow dimension of the bill and obtain thedesired number of samples, at a rapid rate. The use of a wider slit forthe actual sampling also smooths out the output characteristics of thephotodetector and realizes the relatively large magnitude of analogvoltage which is essential for accurate representation and processing ofthe detected reflectance values.

Returning to FIG. 3A, the CPU 30 processes the output of photodetector26 through a peak detector 50 which essentially functions to sample thephotodetector output voltage and hold the highest, i.e., peak, voltagevalue encountered after the detector has been enabled. The peak detectoris also adapted to define a scaled voltage on the basis of which thepattern borderline on bills is detected. The output of the peak detector50 is fed to a voltage divider 54 which lowers the peak voltage down toa scaled voltage V_(S) representing a predefined percentage of this peakvalue. The voltage V_(S) is based upon the percentage drop in outputvoltage of the peak detector as it reflects the transition from the"high" reflectance value resulting from the scanning of the unprintededge portions of a currency bill to the relatively lower "gray"reflectance value resulting when the thin borderline is encountered.Preferably, the scaled voltage V_(S) is set to be about 70-80 percent ofthe peak voltage.

The scaled voltage V_(S) is supplied to a line detector 56 which is alsoprovided with the incoming instantaneous output of the photodetector 26.The line detector 56 compares the two voltages at its input side andgenerates a signal L_(DET) which normally stays "low" and goes "high"when the edge of the bill is scanned. The signal L_(DET) goes "low" whenthe incoming photodetector output reaches the predefined percentage ofthe peak photodetector output up to that point, as represented by thevoltage V_(S). Thus, when the signal L_(DET) goes "low", it is anindication that the borderline of the bill pattern has been detected. Atthis point, the CPU 30 initiates the actual reflectance sampling undercontrol of the encoder 32 (see FIG. 3A) and the desired fixed number ofreflectance samples are obtained as the currency bill moves across theilluminated light strip and is scanned along the central section of itsnarrow dimension.

When master characteristic patterns are being generated, the reflectancesamples resulting from the scanning of a standard bill are loaded intocorresponding designated sections within a system memory 60, which ispreferably an EPROM. The loading of samples is accomplished through abuffered address latch 58, if necessary. During currency discrimination,the reflectance values resulting from the scanning of a test bill aresequentially compared, under control of the correlation program storedwithin the memory unit 38, with each of the corresponding mastercharacteristic patterns stored within the EPROM 60, again through theaddress latch 58. The procedure for scanning bills and generatingcharacteristic patterns is described in U.S. Pat. No. 5,295,196 referredto and incorporated by reference in its entirety above.

The optical sensing and correlation technique described in U.S. Pat. No.5,295,196 permits identification of pre-programmed currencydenominations with a high degree of accuracy and is based upon arelatively short processing time for digitizing sampled reflectancevalues and comparing them to the master characteristic patterns. Theapproach is used to scan currency bills, normalize the scanned data andgenerate master patterns in such a way that bill scans during operationhave a direct correspondence between compared sample points in portionsof the bills which possess the most distinguishable printed indicia. Arelatively low number of reflectance samples is required in order to beable to adequately distinguish among several currency denominations.

In currency discrimination systems in which discrimination is based onthe comparison of a pattern obtained from scanning a subject bill tostored master patterns corresponding to various denominations, thepatterns which are designated as master patterns significantly influencethe performance characteristics of a discrimination system. For example,in the system described in U.S. Pat. No. 5,295,196, the correlationprocedure and the accuracy with which a denomination is identifieddirectly relates to the degree of correspondence between reflectancesamples on the test pattern and corresponding samples on the storedmaster patterns. In other systems, master patterns have been produced byscanning a genuine bill for a given denomination and storing theresulting pattern as the master pattern for that denomination. However,due to variations among genuine bills, this method is likely to resultin poor performance of the discrimination system by rejecting anunacceptable number of genuine bills. It has been found that therelative crispness, age, shrinkage, usage, and other characteristics ofa genuine bill can effect the resulting pattern generated by scanning.These factors are often interrelated. For example, it has been foundthat currency bills which have experienced a high degree of usageexhibit a reduction in both the narrow and wide dimensions of the bills.This shrinkage of "used" bills which, in turn, causes correspondingreductions in their narrow dimensions, can possibly produce a drop inthe degree of correlation between such used bills of a givendenomination and the corresponding master patterns.

As a result, a discrimination system which generates a master patternbased on a single scan of a genuine bill is not likely to performsatisfactorily. For example, if the $20 master pattern is generated byscanning a crisp, genuine $20 bill, the discrimination system may rejectan unacceptable number of genuine but worn $20 bills. Likewise, if the$20 master pattern is generated using a very worn, genuine $20 bill, thediscrimination system may reject an unacceptable number of genuine butcrisp $20 bills.

According to the present invention, a master pattern for a givendenomination is generated by averaging a plurality of componentpatterns. Each component pattern is generated by scanning a genuine billof the given denomination.

According to a first method, master patterns are generated by scanning astandard bill a plurality of times, typically three (3) times, andobtaining the average of corresponding data samples before storing theaverage as representing a master pattern. In other words, a masterpattern for a given denomination is generated by averaging a pluralityof component patterns, wherein all of the component patterns aregenerated by scanning a single genuine bill of "standard" quality of thegiven denomination. The "standard" bill is a slightly used bill, asopposed to a crisp new bill or one which has been subject to a highdegree of usage. Rather, the standard bill is a bill of good to averagequality. Component patterns generated according to this first methodsare illustrated in FIGS. 4A-C. More specifically, FIGS. 4A-C show threetest patterns generated, respectively, for the forward scanning of a $1bill along its green side, the reverse scanning of a $2 bill on itsgreen side, and the forward scanning of a $100 bill on its green side.It should be noted that, for purposes of clarity the test patterns inFIGS. 4A-C were generated by using 128 reflectance samples per billscan, as opposed to the preferred use of only 64 samples. The markeddifference existing among corresponding samples for these three testpatterns is indicative of the high degree of confidence with whichcurrency denominations may be called using the foregoing optical sensingand correlation procedure.

According to a second method, a master pattern for a given denominationis generated by scanning two or more standard bills of standard qualityand obtaining a plurality of component patterns. These componentpatterns are then averaged in deriving a master pattern. For example, ithas been found that some genuine $5 bills have dark stairs on theLincoln Memorial while other genuine $5 bills have light stairs. Tocompensate for this variation, standard bills for which componentpatterns are derived may be chosen with at least one standard billscanned having dark stairs and with at least one standard bill havinglight stairs.

It has been found that an alternate method can lead to improvedperformance in a discrimination systems, especially with regards tocertain denominations. For example, it has been found that the printedindicia on a $10 bill has changed slightly with 1990 series billsincorporating security threads. More specifically, 1990 series $10 billshave a borderline-to-borderline dimension which is slightly greater thanprevious series $10 bills. Likewise it has been found that the scannedpattern of an old, semi-shrunken $5 bill can differ significantly fromthe scanned pattern of a new $5 bill.

According to a third method, a master pattern for a given denominationis generated by averaging a plurality of component patterns, whereinsome of the component patterns are generated by scanning one or more newbills of the given denomination and some of the component patterns aregenerated by scanning one or more old bills of the given denomination.New bills are bills of good quality which have been printed in recentyears and have a security thread incorporated therein (for thosedenominations in which security threads are placed). New bills arepreferably relatively crisp. A new $10 bill is preferably a 1990 seriesor later bill of very high quality, meaning that the bill is in nearmint condition. Old bills are bills exhibiting some shrinkage and oftensome discoloration. Shrinkage may result from a bill having beensubjected to a relatively high degree of use. A new bill utilized inthis third method is of higher quality than a standard bill of theprevious methods, while an old bill in this third method is of lowerquality than a standard bill.

The third method can be understood by considering Table 1 whichsummarizes the manner in which component patterns are generated for avariety of denominations.

                  TABLE 1                                                         ______________________________________                                        Component Scans by Denomination                                               Denomination                                                                           Scan Direction                                                                            CP1      CP2     CP3                                     ______________________________________                                        $1       Forward     -0.2 std 0.0 std +0.2 std                                $1       Reverse     -0.2 std 0.0 std +0.2 std                                $2, left Forward     -0.2 std -0.15 std                                                                             -0.1 std                                $2, left Reverse     -0.2 std -0.15 std                                                                             -0.1 std                                $2, right                                                                              Forward     0.0 std  +0.1 std                                                                              +0.2 std                                $2, right                                                                              Reverse     0.0 std  +0.1 std                                                                              +0.2 std                                $5       Forward     -0.2 old 0.0 new +0.2 old                                                     (lt str) (dk str)                                                                              (lt str)                                $5       Reverse     -0.2 old 0.0 new +0.2 old                                                     (lt str) (dk tr) (lt str)                                $10, left                                                                              Forward     -0.2 old -0.1 new                                                                              0.0 old                                 $10, left                                                                              Reverse     0.0 old  +0.1 new                                                                              +0.2 old                                $10, right                                                                             Forward     +0.1 old +0.2 new                                                                              +0.3 old                                $10, right                                                                             Reverse     -0.2 old -0.15 new                                                                             -0.1 old                                $20      Forward     -0.2 old 0.0 new +0.2 old                                $20      Reverse     -0.2 old 0.0 new +0.2 old                                $50      Forward     -0.2 std 0.0 std +0.2 std                                $50      Reverse     -0.2 std 0.0 std +0.2 std                                $100     Forward     -0.2 std 0.0 std +0.2 std                                $100     Reverse     -0.2 std 0.0 std +0.2 std                                ______________________________________                                    

Table 1 summarizes the position of the scanhead relative to the centerof the green surface of U.S. currency as well as the type of bill to bescanned for generating component patterns for various denominations. Thethree component patterns ("CP") for a given denomination and for a givenscan direction are averaged to yield a corresponding master pattern. Theeighteen (18) rows correspond to the preferred method of storingeighteen (18) master patterns. The scanhead position is indicatedrelative to the center of the borderlined area of the bill. Thus aposition of "0.0" indicates that the scanhead is centered over thecenter of the borderlined area of the bill. Displacements to the left ofcenter are indicated by negative numbers, while displacements to theright are indicated by positive numbers. Thus a position of "-0.2"indicates a displacement of 2/10ths of an inch to the left of the centerof a bill, while a position of "+0.1" indicates a displacement of1/10ths of an inch to the right of the center of a bill.

Accordingly, Table 1 indicates that component patterns for a $20 billscanned in the forward direction are obtained by scanning an old $20bill 2/10ths of a inch to the right and to the left of the center of thebill and by scanning a new $20 bill directly down the center of thebill. FIG. 5A is a graph illustrating these three patterns. These threepatterns are then averaged to obtain the master pattern for a $20 billscanned in the forward direction. FIG. 5B is a graph illustrating anpattern for a $20 bill scanned in the forward direction derived byaveraging the patterns of FIG. 5A. This pattern becomes thecorresponding $20 master pattern after undergoing normalization. Ingenerating the master patterns, one may use a scanning device in which abill to be scanned is held stationary and a scanhead is moved over thebill. Such a device permits the scanhead to be moved laterally, left andright, over a bill to be scanned and thus permits the scanhead to bepositioned over the area of the bill which one wishes to scan, forexample, 2/10ths of inch to the left of the center of the borderlinedarea.

As discussed above, for $10 bills two patterns are obtained in each scandirection with one pattern being scanned slightly to the left of thecenter and one pattern being scanned slightly to the right of thecenter. For $5 bills, it has been found that some $5 bills are printedwith darker stairs ("dk str") on the picture of the Lincoln Memorialwhile others are printed with lighter stairs ("lt str"). The effect ofthis variance is averaged out by using an old bill having light stairsand a new bill having dark stairs.

As can be seen from Table 1, for some bills, the third method of usingold and new bills is not used; rather, a standard ("std") bill is usedfor generating all three component patterns as with the first method.Thus, the master pattern for a $1 bill scanned in the forward directionis obtained by averaging three component patterns generated by scanninga standard bill three times, once 2/10ths of an inch to the left, oncedown the center, and once 2/10ths of an inch to the right.

As illustrated by Table 1, a discrimination system may employ acombination of the developed methods of this invention wherein, forexample, some master patterns are generated according the first methodand some master patterns are generated according to the third method.Likewise, a discrimination system may combine the scanning of new,standard, and old bills to generate component patterns to be averaged inobtaining a master pattern. Additionally, a discrimination system maygenerate master patterns by scanning bills of various qualities and/orhaving various characteristics and then averaging the resultantpatterns. Alternatively, a discrimination system may scan multiple billsof a given quality for a given denomination, e.g., three new $50 bills,while scanning one or more bills of a different quality for a differentdenomination, e.g., three old and worn $1 bills, to generate componentpatterns to be averaged in obtaining master patterns.

While the present invention has been described with reference to one ormore particular embodiments, those skilled in the art will recognizethat many changes may be made thereto without departing from the spiritand scope of the present invention, which is set forth in the followingclaims.

We claim:
 1. An improved method of generating a master patterncorresponding to a given denomination for use in a discrimination systemcapable of discriminating among currency bills of differentdenominations, comprising the steps of:generating a plurality ofcomponent patterns for a given denomination by scanning at least onegenuine bill of said given denomination; and generating a master patternfor said given denomination, said master pattern being derived from anaverage of said component patterns; said component patterns representinganalog variations in characteristic information detected from a genuinebill during scanning, said master pattern representing an average ofanalog variations of said characteristic information for said givendenomination; wherein said plurality of component patterns for a givendenomination are generated by scanning a single genuine bill of saidgiven denomination a plurality of times.
 2. The method of claim 1wherein said single genuine bill is selected to be of standard oraverage quality.
 3. The method of claim 1 wherein said single genuinebill is selected to be of new quality.
 4. An improved method ofgenerating a master pattern corresponding to a given denomination foruse in a discrimination system capable of discriminating among currencybills of different denominations, comprising the steps of:generating aplurality of component patterns for a given denomination by scanning atleast one genuine bill of said given denomination; and generating amaster pattern for said given denomination, said master pattern beingderived from an average of said component patterns; said componentpatterns representing analog variations in characteristic informationdetected from a genuine bill during scanning, said master patternrepresenting an average of analog variations of said characteristicinformation for said given denomination; wherein said plurality ofcomponent patterns for a given denomination are generated by scanningtwo or more genuine bills of said given denomination and wherein saidtwo or more genuine bills are selected to be of the same quality;wherein at least one of said component patterns is generated by scanningone of said genuine bills along a path laterally displaced from the pathalong which at least one other of said genuine bills is scanned ingenerating another of said component patterns.
 5. An improved method ofgenerating a master pattern corresponding to a given denomination foruse in a discrimination system capable of discriminating among currencybills of different denominations, comprising the steps of:generating aplurality of component patterns for a given denomination by scanning atleast one genuine bill of said given denomination; and generating amaster pattern for said given denomination, said master pattern beingderived from an average of said component patterns; said componentpatterns representing analog variations in characteristic informationdetected from a genuine bill during scanning, said master patternrepresenting an average of analog variations of said characteristicinformation for said given denomination; wherein said plurality ofcomponent patterns for a given denomination are generated by scanningtwo or more genuine bills of said given denomination and wherein atleast two of said two or more genuine bills are selected to be ofdifferent qualities; wherein at least one of said two or more genuinebills is selected to be an old bill and at least one of said two or moregenuine bills is selected to be a new bill.
 6. An improved method ofgenerating a master pattern corresponding to a given denomination foruse in a discrimination system capable of discriminating among currencybills of different denominations, comprising the steps of:generating aplurality of component patterns for a given denomination by scanning atleast one genuine bill of said given denomination; and generating amaster pattern for said given denomination, said master pattern beingderived from an average of said component patterns; said componentpatterns representing analog variations in characteristic informationdetected from a genuine bill during scanning, said master patternrepresenting an average of analog variations of said characteristicinformation for said given denomination; wherein said plurality ofcomponent patterns for a given denomination are generated by scanningtwo or more genuine bills of said given denomination and wherein atleast two of said two or more genuine bills are selected to be ofdifferent qualities; wherein at least one of said component patterns isgenerated by scanning one of said genuine bills along a path laterallydisplaced from the path along which at least one other of said genuinebills is scanned in generating another of said component patterns.
 7. Animproved method of generating a master pattern corresponding to a givendenomination for use in a discrimination system capable ofdiscriminating among currency bills of different denominations,comprising the steps of:generating a plurality of component patterns fora given denomination by scanning at least one genuine bill of said givendenomination; and generating a master pattern for said givendenomination, said master pattern being derived from an average of saidcomponent patterns; said component patterns representing analogvariations in characteristic information detected from a genuine billduring scanning, said master pattern representing an average of analogvariations of said characteristic information for said givendenomination; wherein said plurality of component patterns for a givendenomination are generated by scanning two or more genuine bills of saidgiven denomination and wherein said given denomination is a five dollardenomination and wherein said two or more genuine bills are selectedsuch that at least one of said two or more genuine bills has dark stairson a green side and at least one of said two or more genuine bills haslight stairs on a green side.
 8. An improved method of generating amaster pattern corresponding to a given denomination for use in acurrency evaluating device, comprising the steps of:generating aplurality of component patterns for a given denomination by scanning atleast one genuine bill of said given denomination; and generating amaster pattern for said given denomination, said master pattern beingderived from an average of said component patterns; said componentpatterns representing analog variations in characteristic informationdetected from a genuine bill during scanning, said master patternrepresenting an average of analog variations of said characteristicinformation for said given denomination; wherein said plurality ofcomponent patterns for a given denomination are generated by scanning asingle genuine bill of said given denomination a plurality of times. 9.The method of claim 8 wherein said single genuine bill is selected to beof standard or average quality.
 10. The method of claim 8 wherein saidsingle genuine bill is selected to be of new quality.
 11. An improvedmethod of generating a master pattern corresponding to a givendenomination for use in a currency evaluating device, comprising thesteps of:generating a plurality of component patterns for a givendenomination by scanning at least one genuine bill of said givendenomination; and generating a master pattern for said givendenomination, said master pattern being derived from an average of saidcomponent patterns; said component patterns representing analogvariations in characteristic information detected from a genuine billduring scanning, said master pattern representing an average of analogvariations of said characteristic information for said givendenomination; wherein said plurality of component patterns for a givendenomination are generated by scanning two or more genuine bills of saidgiven denomination and wherein said two or more genuine bills areselected to be of the same quality; wherein at least one of saidcomponent patterns is generated by scanning one of said genuine billsalong a path laterally displaced from the path along which at least oneother of said genuine bills is scanned in generating another of saidcomponent patterns.
 12. An improved method of generating a masterpattern corresponding to a given denomination for use in a currencyevaluating device, comprising the steps of:generating a plurality ofcomponent patterns for a given denomination by scanning at least onegenuine bill of said given denomination; and generating a master patternfor said given denomination, said master pattern being derived from anaverage of said component patterns; said component patterns representinganalog variations in characteristic information detected from a genuinebill during scanning, said master pattern representing an average ofanalog variations of said characteristic information for said givendenomination; wherein said plurality of component patterns for a givendenomination are generated by scanning two or more genuine bills of saidgiven denomination and wherein at least two of said two or more genuinebills are selected to be of different qualities; wherein at least one ofsaid two or more genuine bills is selected to be an old bill and atleast one of said two or more genuine bills is selected to be a newbill.
 13. An improved method of generating a master patterncorresponding to a given denomination for use in a currency evaluatingdevice, comprising the steps of:generating a plurality of componentpatterns for a given denomination by scanning at least one genuine billof said given denomination; and generating a master pattern for saidgiven denomination, said master pattern being derived from an average ofsaid component patterns; said component patterns representing analogvariations in characteristic information detected from a genuine billduring scanning, said master pattern representing an average of analogvariations of said characteristic information for said givendenomination; wherein said plurality of component patterns for a givendenomination are generated by scanning two or more genuine bills of saidgiven denomination and wherein at least two of said two or more genuinebills are selected to be of different qualities; wherein at least one ofsaid component patterns is generated by scanning one of said genuinebills along a path laterally displaced from the path along which atleast one other of said genuine bills is scanned in generating anotherof said component patterns.
 14. An improved method of generating amaster pattern corresponding to given denomination for use in a currencyevaluating device, comprising the steps of:generating a plurality ofcomponent patterns for a given denomination by scanning at least onegenuine bill of said given denomination; and generating a master patternfor said given denomination, said master pattern being derived from anaverage of said component patterns; said component patterns representinganalog variations in characteristic information detected from a genuinebill during scanning, said master pattern representing an average ofanalog variations of said characteristic information for said givendenomination; wherein said plurality of component patterns for a givendenomination are generated by scanning two or more genuine bills of saidgiven denomination and wherein said given denomination is a five dollardenomination and wherein said two or more genuine bills are selectedsuch that at least one of said two or more genuine bills has dark stairson a green side and at least one of said two or more genuine bills haslight stairs on a green side.
 15. An improved method of generatingmaster patterns for discrimination systems capable of discriminatingamong currency bills of different denominations, comprising the stepsof:generating a plurality of component patterns for a plurality ofdenominations by scanning at least one genuine bill of eachdenomination; and generating a master pattern for each denomination,said master patterns being derived from an average of said componentpatterns generated for each corresponding denomination; said componentpatterns representing analog variations in characteristic informationdetected from a genuine bill during scanning, said master patternrepresenting an average of analog variations of said characteristicinformation for said given denomination; wherein said plurality ofcomponent patterns for a given denomination are generated by scanning asingle genuine bill of said given denomination a plurality of times. 16.An improved method of generating master patterns for discriminationsystems capable of discriminating among currency bills of differentdenominations, comprising the steps of:generating a plurality ofcomponent patterns for a plurality of denominations by scanning at leastone genuine bill of each denomination; and generating a master patternfor each denomination, said master patterns being derived from anaverage of said component patterns generated for each correspondingdenomination; said component patterns representing analog variations incharacteristic information detected from a genuine bill during scanning,said master pattern representing an average of analog variations of saidcharacteristic information for said given denomination; wherein saidplurality of component patterns for a given denomination are generatedby scanning two or more genuine bills of said given denomination andwherein at least one of said two or more genuine bills is selected to bean old bill and at least one of said two or more genuine bills isselected to be a new bill.
 17. An improved method of generating masterpatterns for discrimination systems capable of discriminating amongcurrency bills of different denominations, comprising the stepsof:generating a plurality of component patterns for a plurality ofdenominations by scanning at least one genuine bill of eachdenomination; and generating a master pattern for each denomination,said master patterns being derived from an average of said componentpatterns generated for each corresponding denomination; said componentpatterns representing analog variations in characteristic informationdetected from a genuine bill during scanning, said master patternrepresenting an average of analog variations of said characteristicinformation for said given denomination; wherein said plurality ofcomponent patterns for a given denomination are generated by scanningtwo or more genuine bills of said given denomination and wherein atleast one of said component patterns is generated by scanning one ofsaid genuine bills along a path laterally displaced from the path alongwhich at least one other of said genuine bills is scanned in generatinganother of said component patterns.
 18. An improved method fordiscriminating among currency bills of different denominations,comprising the steps of:illuminating a predetermined section of acurrency bill by focusing at least one strip of light thereupon;detecting the light reflected off said illuminated section of said billto generate an analog reflectance signal; generating relativedisplacement between said strip of light and said currency bill so as toilluminate or optically scan successive sections of said bill along apredetermined dimension thereof; obtaining a series of analogreflectance signals corresponding to light reflected from each of saidsuccessive bill sections using said strip of light; digitizing andprocessing said series of analog reflectance signals to yield a set ofdigital data samples which, in combination, represent a data patterncharacteristic of the currency denomination of said bill; generating andstoring a set of master characteristic patterns corresponding to opticalscanning of genuine bills of each of the different currencydenominations to be discriminated, said master patterns corresponding tosaid different denominations being derived from an average of aplurality of component patterns for each of said differentdenominations, said component patterns for a given denomination beingderived by scanning two or more genuine bills corresponding to saidgiven denomination, wherein at least one of said two or more genuinebills is selected to be an old bill and at least one of said two or moregenuine bills is selected to be a new bill; and comparing thecharacteristic pattern for a scanned currency bill to each of saidstored master patterns to determine the degree of correlationtherebetween, and thereby to identify the denomination of said currencybill.
 19. An improved method for discriminating among currency bills ofdifferent denominations, comprising the steps of:illuminating apredetermined section of a currency bill by focusing at least one stripof light thereupon; detecting the light reflected off said illuminatedsection of said bill to generate an analog reflectance signal;generating relative displacement between said strip of light and saidcurrency bill so as to illuminate or optically scan successive sectionsof said bill along a predetermined dimension thereof; obtaining a seriesof analog reflectance signals corresponding to light reflected from eachof said successive bill sections using said strip of light; digitizingand processing said series of analog reflectance signals to yield a setof digital data samples which, in combination, represent a data patterncharacteristic of the currency denomination of said bill; generating andstoring a set of master characteristic patterns corresponding to opticalscanning of genuine bills of each of the different currencydenominations to be discriminated, said master patterns corresponding tosaid different denominations being derived from an average of aplurality of component patterns for each of said differentdenominations, said component patterns for a given denomination beingderived by scanning two or more genuine bills corresponding to saidgiven denomination, wherein at least one of said component patterns isgenerated by scanning one of said genuine bills along a path laterallydisplaced from the path along which at least one other of said genuinebills is scanned in generating another of said component patterns; andcomparing the characteristic pattern for a scanned currency bill to eachof said stored master patterns to determine the degree of correlationtherebetween, and thereby to identify the denomination of said currencybill.
 20. An improved method of generating a master patterncorresponding to a given denomination for use in a discrimination systemcapable of discriminating among currency bills of differentdenominations, comprising the steps of:generating a plurality ofcomponent patterns for a given denomination by scanning at least onegenuine bill of said given denomination along a given segment with ananalog scanner, said analog scanner generating a signal proportional tocharacteristic information detected from a genuine bill along saidsegment, said signal being sampled at preselected intervals as saidgenuine bill and scanner are moved relative to each other, each of saidsamples being proportional to the detected characteristic informationfor a given portion of said segment; and generating a master pattern forsaid given denomination, said master pattern being derived from anaverage of said component patterns, said master pattern comprisingaverage samples, each of said average samples being an average ofsamples that are proportional to characteristic information along saidsegment; wherein said plurality of component patterns for a givendenomination are generated by scanning two or more genuine bills of saidgiven denomination and wherein said two or more genuine bills areselected to be of the same quality; wherein at least one of saidcomponent patterns is generated by scanning one of said genuine billsalong a path laterally displaced from the path along which at least oneother of said genuine bills is scanned in generating another of saidcomponent patterns.
 21. An improved method of generating a masterpattern corresponding to a given denomination for use in adiscrimination system capable of discriminating among currency bills ofdifferent denominations, comprising the steps of:generating a pluralityof component patterns for a given denomination by scanning at least onegenuine bill of said given denomination along a given segment with ananalog scanner, said analog scanner generating a signal proportional tocharacteristic information detected from a genuine bill along saidsegment, said signal being sampled at preselected intervals as saidgenuine bill and scanner are moved relative to each other, each of saidsamples being proportional to the detected characteristic informationfor a given portion of said segment; and generating a master pattern forsaid given denomination, said master pattern being derived from anaverage of said component patterns, said master pattern comprisingaverage samples, each of said average samples being an average ofsamples that are proportional to characteristic information along saidsegment; wherein said plurality of component patterns for a givendenomination are generated by scanning two or more genuine bills of saidgiven denomination and wherein at least two of said two or more genuinebills are selected to be of different qualities; wherein at least one ofsaid two or more genuine bills is selected to be an old bill and atleast one of said two or more genuine bills is selected to be a newbill.
 22. An improved method of generating a master patterncorresponding to a given denomination for use in a discrimination systemcapable of discriminating among currency bills of differentdenominations, comprising the steps of:generating a plurality ofcomponent patterns for a given denomination by scanning at least onegenuine bill of said given denomination along a given segment with ananalog scanner, said analog scanner generating a signal proportional tocharacteristic information detected from a genuine bill along saidsegment, said signal being sampled at preselected intervals as saidgenuine bill and scanner are moved relative to each other, each of saidsamples being proportional to the detected characteristic informationfor a given portion of said segment; and generating a master pattern forsaid given denomination, said master pattern being derived from anaverage of said component patterns, said master pattern comprisingaverage samples, each of said average samples being an average ofsamples that are proportional to characteristic information along saidsegment; are generated by scanning two or more genuine bills of saidgiven denomination and wherein at least two of said two or more genuinebills are selected to be of different qualities; wherein at least one ofsaid component patterns is generated by scanning one of said genuinebills along a path laterally displaced from the path along which atleast one other of said genuine bills is scanned in generating anotherof said component patterns.
 23. An improved method of generating amaster pattern corresponding to a given denomination for use in adiscrimination system capable of discriminating among currency bills ofdifferent denominations, comprising the steps of:generating a pluralityof component patterns for a given denomination by scanning at least onegenuine bill of said given denomination along a given segment with ananalog scanner, said analog scanner generating a signal proportional tocharacteristic information detected from a genuine bill along saidsegment, said signal being sampled at preselected intervals as saidgenuine bill and scanner are moved relative to each other, each of saidsamples being proportional to the detected characteristic informationfor a given portion of said segment; and generating a master pattern forsaid given denomination, said master pattern being derived from anaverage of said component patterns, said master pattern comprisingaverage samples, each of said average samples being an average ofsamples that are proportional to characteristic information along saidsegment; wherein said plurality of component patterns for a givendenomination are generated by scanning two or more genuine bills of saidgiven denomination and wherein said given denomination is a five dollardenomination and wherein said two or more genuine bills are selectedsuch that at least one of said two or more genuine bills has dark stairson a green side and at least one of said two or more genuine bills haslight stairs on a green side.
 24. An improved method of generating amaster pattern corresponding to a given denomination for use in adiscrimination system capable of discriminating among currency bills ofdifferent denominations, comprising the steps of:generating a pluralityof component patterns for a given denomination by scanning a singlegenuine bill of said given denomination a plurality of times along agiven segment with an analog scanner, said analog scanner generating asignal proportional to characteristic information detected from agenuine bill along said segment, said signal being sampled atpreselected intervals as said genuine bill and scanner are movedrelative to each other, each of said samples being proportional to thedetected characteristic information for a given portion of said segment;and generating a master pattern for said given denomination, said masterpattern being derived from an average of said component patterns, saidmaster pattern comprising average samples, each of said average samplesbeing an average of samples that are proportional to characteristicinformation along said segment.
 25. The method of claim 24 wherein saidsingle genuine bill is selected to be of standard or average quality.26. The method of claim 24 wherein said single genuine bill is selectedto be of new quality.
 27. The method of claim 24 wherein said scanningis optical scanning.
 28. An improved method of generating a masterpattern corresponding to a given denomination for use in a currencyevaluating device, comprising the steps of:generating a plurality ofcomponent patterns for a given denomination by scanning a single genuinebill of said given denomination a plurality of times; and generating amaster pattern for said given denomination, said master pattern beingderived from an average of said component patterns; said componentpatterns representing analog variations in characteristic informationdetected from a genuine bill during scanning, said master patternrepresenting an average of analog variations of said characteristicinformation for said given denomination.
 29. An improved method ofgenerating a master pattern corresponding to a given denomination foruse in a currency evaluating device, comprising the steps of:generatinga plurality of component patterns for a given denomination by scanningtwo or more genuine bill of said given denomination; and generating amaster pattern for said given denomination, said master pattern beingderived from an average of said component patterns; wherein said givendenomination is a five dollar denomination and wherein said two or moregenuine bills are selected such that at least one of said two or moregenuine bills has dark stairs on a green side and at least one of saidtwo or more genuine bills has light stairs on a green side.
 30. Animproved method of generating a master pattern corresponding to a givendenomination for use in a currency evaluating device, comprising thesteps of:generating a plurality of component patterns for a givendenomination by scanning a single genuine bill of said givendenomination a plurality of times; and generating a master pattern forsaid given denomination, said master pattern being derived from anaverage of said component patterns.
 31. The method of claim 30 whereinsaid single genuine bill is selected to be of standard or averagequality.
 32. The method of claim 30 wherein said single genuine bill isselected to be of new quality.
 33. The method of claim 30 wherein saidscanning is optical scanning.